ST120 Quad

ST120 Quad Detector circuit overlay

ST120 Quad Detector circuit overlay

ST120 Quad Thermopile Detector

ST120 Quad Thermopile Detector

A four-channel silicon-based thermopile in a TO-5 package. Each small active area is 1.2mm x 1.2mm . Time constant of 25ms with Nitrogen encapsulation gas. Delivers a very low Temperature Coefficient of Responsivity of -0.04%/°C. This detector has a very short thermal shock response to ambient temperature change.

Excellent for gas analysis, position sensor, and horizon sensor.

Low cost with high output.


  1. See Standard Windows and Filters (PDF) for list of optical filter options
  2. Internal 30kΩ 5% NTC chip thermistor provides ambient package temperature measurement. See DC-4005 section of Thermistor Options (PDF).
  3. Internal aperture precisely defines active area for applications with FOV and/or spot size requirements. See Aperture Options (PDF) for available sizes.
  4. See Thermopile Configuration Table for more options.

For more detailed information see the datasheet ST120 Quad (PDF).

Parameter Min Typical Max Symbol Units Comments
Active Area size   1.2 x 1.2   AA mm Hot junction size, per element.
Element Area   1.44   A mm2  
Number of Junctions   80       Per element.
Number of Channels   4       Per detector package.
Output Voltage   140   Vs μV DC,  H=330μW/cm2 (3)
Signal-to-Noise Ratio   3,649   SNR √Hz DC, SNR=Vs/Vn
Responsivity   29.5   V/W DC, =Vs/HA  (2)
Resistance   90   R Detector element
Temperature Coefficient of   -.04     %/°C Best linear fit, 0° to 85°C (1)
Temperature Coefficient of  R   .02     %/°C Best fit, 0° to 85°C (1)
Noise Voltage   38.4   Vn nV/√Hz Vn2=4kTR
Noise Equivalent Power   1.30   NEP nW/√Hz DC,  NEP= VnHA/Vs (2)
Detectivity   0.92   D* 108√Hz/W DC,  D*=Vs/ VnH√A  (2)
Time Constant   25   Τ ms Chopped, -3dB point (1)
Field of View   9°/63°   FOV Degrees See Assembly Drawings for FOV Description.
Package Type   TO-5       Standard package hole size: Ø.150"
Element Matching   25   M % M=|VA-VB|/VB (2)
Element Separation   2.08     mm Center to Center
Operating Temperature -50   125 Ta °C  

General Specifications: 
Flat spectral response from 100nm to > 100µm.  Linear signal output from 10-6 to 0.1W/cm2
Maximum incident radiance 0.1W/cm2 , damage threshold ≥ .5W/cm2
(1) Parameter is not 100% tested. 90% of all units meet these specifications.
A is detector area in cm2.
Test Conditions: 500K Blackbody source; Detector active surface 10cm from 0.6513cm Diameter Blackbody Aperture.

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